I cant open my mouth wide enough, 1 finger can only enter my mouth, it started when my lower wisdom tooth hurts and become swollen about 4 months ago?

See dentist ASAP: Your mouth should open wide enough for minimum 2 fingers. It seems like you have trismus caused by infection around the gum surrounding your wisdom tooth. We call this type of infection pericoronitis. It can lead to serious health problem. You should be on antibiotics. Please see your dentist immediately and also have your tooth extracted.

TMJ: Without an actual examination, I cannot give specific medical advice on your particular health,but the standard description of temporal mandibular joint is like this. http://my.clevelandclinic.org/head-neck/diseases-conditions/hic-tmd-disorders.aspx

See doctor/dentist: If it's still swollen, and if you have any swollen glands in your neck, you should see a dentist or family doctor soon to make sure there isn't an ongoing infection or other source of inflammation in your mouth, like TMJ. Oral cancers are fairly rare at your age, but have been on the increase recently, which is one more reason to have your mouth thoroughly checked.